Air control instrument



Aug. 3, 1943. c. B. MOORE AIR-ONTROL INSTRUMENT Z Sheets-Sheet 1 FiledOct. 24, 1939 INVENTOR. COLEMAN 8 MORE ATTORNEY 3, 1943. c, MOQRE$325,957

AIR CONTROL INSTRUMENT Filed Oct. 24, 1939 2 Sheets-Sheet 2 FIGZ vPatented Aug. 3, 1943 AIR coN'moL INSTRUMENT Coleman B. Moore, CarrollPark, Pa., assignor to The Brown Instrument Company, Philadelphia, Pa.,a corporation of Pennsylvania Application October 24, 1939, Serial No.300,961

Claims. (01

The present invention relates to air control apparatus of the typecomprising an element deflr cting in accordance with changes in thevalue oi av controlling quantity or condition which may be pressure,temperature or other measurable variable, and means through whichdeflection of said element from the predetermined or normal valueposition of the element varies an air or other fiuid pressureconstituting a control force, and simple and efiective fluid pressuremeans through which variation in saidcontrol force modifies the actionof said element on the first mentioned means so as to effect suitablecorrective variations in the control torce on a departure of the latterfrom its predetermined or normal value, without creating anobjectionable tendency to unstable control or hunting.

A specific object ofthe present invention is to provide a control actionin which a relatively large initial kick or control action may be madeon a change in a controlling quantity, while avoiding the tendency tohunting which would result from such a large initial adjustment if thecontrol system did not include provisions for a suitable subsequentfollow-up adjustment. In accordance with the present invention, theperiod of each initial kick effect is prolonged by provisions which aremade for delaying the succeeding follow-up adjustment.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, its advantages and specific objects obtained with its use,reference should be had to the accompanying drawings and descriptivematter in which I have illustrated and described a preferred embodimentof the invention.

In the drawings:

Fig. l is a view of a control system embodying one form of my invention;I

Fig. 2 is a view of another embodiment; and

Fig. 3 is another embodiment in which the follow-up is producedhydraulically. Referring first to Fig. 1 where there is shown by way ofexample, a temperature control systerm. A heater l whose temperature isto be regulated has it changed by varying the fiow of a heating fiuidthereto through a pipe 2 by an air controlled valve 3. This valve isprovided with a diaphragm upon which varying air pressures are appliedto'chang its opening in a well known manner, an increase in pressureserving to open the valve. Located within the furnace and subject to thetemperature thereof is a bulb 4, filled with a liquid that expands uponan increase in temperature. This bulb is connected by a capillary 5 withthe fixed end of a Bourdon tube 6 in the form of a helix. This tubeunwinds upon an increase in pressure therein to move a lever I, fastenedto its free end, around an axis 8 in a counter-clockwise direction upona decrease in temperature and in a clockwise direction upon an increasein the temperature of the heater 1.

Movement of the lever 1, through a link 9, rocks a bellcrank l0 aroundits pivot II and through the link I2 pivots a lever l3 around a supportl4. As the lever [3 moves it adjusts a flapper valve l5 relative to anozzle iii a vary the pressure applied to the diaphragm of valve 3 in amanne presently to'vbe described. The

flapper I5 is pivoted at I! and has a natural bias toward the nozzle l6,which bias is overcome by a pin [8 on one arm of a bellcrank [9,

pivoted at 20 on a lever 2i that is also pivoted at H. The second arm ofbellcrank I9 is attached to and moved by the lever l3.

The flapper I5 is also moved by movement of the lever 2| by means of alink 22 attached .to an extension of a movable plate 23. This plate isattached to the ends of a pair of opposed bellows 24'and 25. The formerof these is fixed to a plate 26 that has an opening 21 therethroughcommunicating with the atmosphere, which opening is adjusted by arestrictor 28. The second bellows 25 has its other end attached to aplate 29 that has an ,opening therein communicating with a pipe 30.

Air is supplied to the nozzle I6 and the valve 3 from a supply line 3i,past a restriction 32, and this same pressure is applied throughanextension of line 3| to the interior of a bellows 33 that has its lowerend supported by a plate 34. The upper end of bellows 33 is attached toa movable plate 35, whose movement, along with that of bellows 33 isopposed by a second bellows 36 that has its upper end fixed to a plate31. The plate 31 is provided with an opening by means of which the line30 may communicate with the interior of bellows 36. The interiors ofbellows 34 and 36 are in communications by means of a pipe 38 that haswithin it an adjustable restriction 39.

Initial expansion or contraction of the bellows 33, when the pressurewithin it is changed is delayed by means of a spring 40 that acts on alever M which is pivoted to the plate 35. The lever M is provided withtwo fulcrum points that In the operation of the instrument upon, for

example, a decrease in the temperature of the heater I the Bourdon tubeii will contract and shift link 9 to the left. This will, through theconnected lever and link mechanism, move pin are formed by pins 42 and43 which receivemined by experiment. The over-correction of the valve,or initial effect as it is'often called, and.

the gradual removal of the over-correction permits the departure fromnormal of the tempera- .ture to be quickly checked, with a rapid returnto normal.

In order to control the temperature at different normal values it isnecessary to adjust the initial position of flapper l5, relative to thenozzle I6. This may be accomplished by shifting th supporting link I4 tochange the fulcrum point of l8 to the right permitting the flapper l5 tomove toward the nozzl I6 throttling the flow therethrough and increasingthe pressure in the line 3|. Such an increase. in pressure builds up onthe diaphragm of valve 3 to open that valve and permit more heatingfluid to flow to the heater I. At the same time pressure builds up inthe bellows 33, but has no immediate effect thereon. When, however, thepressure in the bellows 33 is suflicient to overcome the force of spring40 that bellows w ll expand and correspond ngly compress the bellows 36,forcing air therefrom through line 30 into bellows 25 to correspondinglyexpand the latter. I

Expansion of bellows 25 moves plate 23 to the left, and through link 22,pivots the lever 21 carrying the bell-crank l9 clockwise so that the pinill will move the flapper l5 away from the nozzle I6, preventing anyfurther increase in the valve pressure. The movement of the plate 23 tothe left compresses bellows 24, increasing the pressure there n abovethat of the atmosphere.-

Therefore, air will escape through the open ng 21 at a rate determinedby the set ing of restrictor the nozzle as a result of the follow-upaction.

Ultimately the valve pressure is slightly higher 'than it originallywas, to overcome the initial decrease in the temperature of the heater.

It must be remembered that while in the above description the variouspressure changes have been described in sequence they are actuallycontinuous; As the flapper starts its initial movement the pressuresbegin to change, building up on the valve d aphragm to a maximumdetermined by the setting of the spring 40 and then gradually reducingat a ratedependent upon the adjustment of the restrictions 39 and 28. Inthis manner upon the occurrence of a change in the value of the heatertemperature the valve 3 is either opened or closed, depending upon thedirection of the deviation, an amount in excess of that ncessary toreturn the condition to normal.

' The valve is then gradually returned to a position necessary tomaintain the temperature at normal at a rate dependent upon the rate oi.change of the heater. This rate adjustment may be made in the fieldafter the particular rate of temperature change of the heater has b endeter:

lever l3. To ths end the upper end of link I4 is pivoted to one arm of abellcrank 4'! that is also pivoted at H. The second arm of the bellcrank41 is connected by a link 48 to a crank 49 attached to a knob 50. Inorder to lower the control point, knob 50 will be rotated in acounterclockwise direction to move the parts into their dotted linepositions. Thus flapper I5 is moved away from the nozzle 16, decreasngthe pressure on valve 3. The valve will thereby close to permit lessheating fluid to flow through pipe 2 and reduce the temperature of theheater.

Referring to Fig. 2 there is shown another type of mechanism foraccomplishing the results of the instrument of Fig. 1. In thisembodiment the follow-up motion of the flapper is followed by a reverseor compensating movement thereof. The l nk 22 in this case is attachedat its right end to a support 5| that is rig dly fastened to a rod 52,each end of which is attached to the movable end wall of a bellows 53 or54. The bellows 53 is fastened to a supporting plate 55 and along withasecond bellows 56 forms a chamber 51 that is filled with liquid. Thebellows 56 is surrounded by a cup-shaped protecting casing 53 that hasan opening in it so that the exterior of the bellows 53 is subjected toatmospheric pressures,

Inga like manner the b llows 54 is surrounded by a bellows 59 whichforms a chamber 50 that is liquid filled and in communication with thechamber 51 by means of a pipe 6| having an adjustable restricton 52 init. The bellows 54 and 59 are attached to a supporting plate 53 thatalso has attached to it and surrounding the bellows 59 a cup-shapedcasing 54. The interior of this casing is connected with the interior ofthe bellows 35 by means of the pipe 30.

In the operation of this embodiment upon a decrease in the temperatureof the heater the flapper l5 w ll move toward the nozzle l9 to throttlethe flow therethrough. This builds up the pressure on the valvediaphragm to open the valve further and at the same time builds uppressure in the bellows 33 in a mannerLpreviously described. when thepressure in bellows 33 has built up sumciently to overcome the force ofspring 40 the bellows 35 will be compressed and force air'into thecasing 54. When this occurs the l quid in chamber 60 acts as a solidbody and the compression of bellows 59 is transmitted directly to thebellows 54 and through the rod 52 and link 22 to th lever 2|. Thus afollow-up motion tending to neutralize the original pressure change isobtained.

Because of the increased air pressure applied to the bellows 59 theliquid in chamber 50 is under a higher pressure than that in chamber 51.This liquid will therefore flow through the pipe 8| at a rate determinedby the setting of restriction 62 from chamber 60 to chamber 51. As, dueto their natural resiliency, the bellows 53 and 54 resume their normallengths the link 22 will be slowly shifted to the right to bring theflapper l5 parts 33 to 46 of those figures.

back toward its original position. Ultimately the flapper will come torest at substantially its original point with an increased pressure inthe system over that which was therein at the beginning of the change intemperature to compensate for the increase in load on the heater thatcaused the original temperature drop.

With this form of the invention, as in that of Fig. 1, the initiallylarge increase in valve pressure produced in order to overcome thetension of spring 40 causes an opening of the valve 3 beyond that neededto correct the temperature change and a gradual closing of the valve tothe correct point. Therefore, the temperature is rapidly brought back tonormal.

The apparatus shown in Fig. 3 may be used with the flapper actuatingmechanism of either Fig. 1 or Fig. 2, in place of the kick producing Asshown, the apparatus of this figure produces the follow-up movement ofthe flapper l5 hydraulically rather than pneumatically as was previouslydescribed. To this end the bellows 25 of Fig. 1, if it is used with thatapparatus or the space between bellows 59 and casing 64 if it is usedwith the apparatus of Fig. 2, must be filled with liquid. This, in somecases, is desirable since compression of the liquid is immediatelytransferred from one point to another, while a short lag may be producedwhile the pressure of a gas is building up in one place as a result ofcompression in another.

In this form the line 3|, which is subjected to the valve pressure,leads to a chamber 65 formed between a cup-shaped casing 66 anda bellows61, both of which are attached to a stationary supporting plate 68. Theinterior of the bellows 61 is filled with liquid and communicates withthe interior of another bellows 69 that is attached at one end to theplate 68 and at its other end to a movable plate 10. The plate I0 isconnected communicates with the interior of bellows 61 through a pipe"having an adjustable restriction in it. This pipe and restriction servethe same purpose as pipe 38 and restriction 39 of Figs. 1 and 2. Theinterior of bellows 13 also communicates by means of line 30 with thebellows or the chamber formed between bellows 59 and casing 64, as thecase may be.

Instead of using a spring to determine the pressure increase to producethe impulse or kick as was previously described, the magnitude of theimpulse is determined by the pressure in a bellows 16 located betweenthe plates 10 and H. This amounts to a pneumatic spring. The bellows 16has attached to each end a plate 11 or 18, each provided with acup-shaped depression, which plates bear against stationary supports 19and 80, respectively, to limit the expansion of the bellows. The plate10 has attached to and projecting from it a threaded stud 8| which isreceived in the depression of the plate 11. Surrounding the stud 8| is acollar 82 which bears against the plate I! to limit upward movement ofplate Ill with respect thereto. In a like manner downward movement ofplate 'll relative to plate 18 is limited by a stud 86 that extends fromplate H into the depression of plate 18 and is surrounded by a collar 83that bears against the lower plate. The pressure in the bellows 16 isadjusted by a pressure regulator 84 located in aline 85 leading fromsome suitable source of fluid under pressure to the bellows.

In the operation of this form of the invention an increase in valvepressure willbe transmitted to the chamber 65 through line 3|. As thepressure builds up the bellows 61 will tend to contract forcing liquidinto be1lows69 to expand the latter. This cannot happen, however, untilthe pressure in bellows 69 has increased enough to compress the bellows16. When this occurs upward movement of plate 10 will compress thebellows 1'3, forcing the liquid therein through the pipe 30 to producethe follow-up movement of the flapper l5. contemporaneously with thepressure increase in chamber 65 liquid is flowing at asuitable retardedrate through the pipe 14 to equalize the pressures in bellows 69 and 13.This will not take place, however, until after the pressure in bellows59 has increased sufficiently to compress the bellows 13. The magnitudeof the initial impulse or kick is. determined by the .pressure in thebellows I6 and its duration depends upon the adjustment of restriction.

From the above description it will be apparent that I have invented aninstrument which is capable of magnifying the efiect of a change in thevalue-of a condition from normal on the control element in order toquickly stop the deviation and to quickly return the condition to itsnormal value. This magnified effect is then removed at a rate dependentupon the rate of change of the condition in order to prevent overshooting or hunting thereof.

While in accordance with the provisions of the statutes, I'haveillustrated and described the best form of my invention now known to be,it will be apparent to those skilled in the art that changes may be madein the form of the apparatus disclosed without departing from the spiritof my invention as set forth in the appended claims, and that in somecases certain features of my invention may sometimes be used toadvantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. An air control instrument having a bleed 4 nozzle, a flapper valvetherefor, means responsive to the value of a variable condition torelatively move said flapper and nozzle in either of two directions,fluid operated follow-upprovisions in said air controller to relativelymove said nozzle and flapper in the opposite direction to its originalmovement, a supply of fluid under pressure regulated by said movement, acontrol valve operated by the regulated pressure supply, a pair ofopposed bellows mounted so that expansion of one will producecontraction of the other, spring means to oppose a change in length ofsaid bellows, a fluid connection between said regulated supply of fluidand one of said opposed bellows, a

fluid connection between the other of said 0pposed bellows and saidfluid operated follow-up provisions, and a restricted fluid connectionbetween said bellows.

2. In an air control instrument, a bleed nozzle, a flapper valvetherefor, means responsive'to the value of a condition to move saidflapper relative to said nozzle, fluid operated follow-up provisions insaid control instrument operative to move said flapper relative to saidnozzle as a result of movement thereof by said means and in a directionto oppose the movement imparted by said means, a supply of fluid underpressure to said. nozzle, a control valve operated bythe regulatedpressure supply, a connection'between the regulated pressure supply andsaid fluid operated follow-up provisions including a pair of opposedbellows, adapted to changein length upon the application of pressurethereto, spring means acting to prevent a change in length of saidbellows, a fluid connection between one of said bellows and saidregulated, fluid pressure, a fluid connection between said other bellowsand said'fluid operated follow-up provisions, and

a restricted fluid connection between said bellows.

3, An air control instrument including a port,

a valve for said port, a supply offiair under pressure connected to saidport and adjusted as said fluid connection between said adjusted airpressure and one chamber, a fluid connection between said fluid operatedfollow-up provisions and the dthenof said chambers, a restricted fluidconnection between said chambers, and adjustable spring means to preventexpansion or said chambers until a predetermined pressure change hasoccurred therein. I

4. An air control instrument including a port,

regulated by movement of said flapperrelative a valve therefor, a supplyof air under pressure regulated'by relative movement of said valve andport, a control means operated by the adjusted pressure, a deviceresponsive to changes in a variable condition to move said valverelative to said port, fluid operated follow-up provisions to move saidvalve relative to said port in a direction opposite to and as a resultof a movement produced by said device, means to operate said fluidoperated follow-up provisions pneumatically as a result of a movement ofsaid valve by said device comprising a pair of opposed, expansiblechambers, a fluid connection between one of said chambers and saidadjusted air supply, a fluid connection between the other of saidchambers and said fluid operated follow-up provisions, a restrictedfluid connection between said chambers, and adjustable spring means toresist a change in size in said chambers until a predetermined pressurechange has occurred in one of them. p

5. In an air control instrument, an impulse unit comprising a first anda second bellows each fixedly mounted on one end and attached foropposing movement at their opposite ends, a

- third bellows mounted between the first two bellows, means attached toeach of said first bellows to compress said third bellows upon expansionof either of the first two, means to supply a pressure to said thirdbellows to thereby oppose expansion of either of said first two bellows,means to apply pressure to one of said first or second bellows toovercome the force of the third bellows, means operated by the other ofsaid first or second bellows to prevent an increase of the pressurebeyond a predetermined point, and means to gradually reduce saidpressure.

COLEMAN B. MOORE.

